Characterization of SEI layers on LiMn2O4 cathodes with in situ spectroscopic ellipsometry

In situ spectroscopic ellipsometry was employed to study the initial stage of solid electrolyte interphase (SEI) layer formation on thin-film LiMn2O4 electrodes. The SEI layer formed immediately upon exposure of the electrode to ethylene carbonate/dimethyl carbonate (1:1 by vol) 1.0 M LiPF6 electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles. (c) 2005 The Electrochemical Society.